by Knowledge » Mon Apr 09, 2018 8:21 pm
Reading your post, it seems like you are thinking about the battery, but not so much about the business of keeping the battery charged-up.
The simple answer is a small burglar alarm battery as this would supply enough power to keep the light working for a while, but to keep the battery topped up, you will need to get a DC supply from the engine.
I guess your electrical system is AC, so there would be some simple modifications to top-up the battery.
If I have read too much into your question, let us know. If you want to learn more about running a battery, or alternative ways to power your pathfinder, get back to us.